1. Field of the Invention
The present invention relates to a vacuum pump for use in a semiconductor manufacturing apparatus, an electron microscope, a surface analysis apparatus, a mass spectrograph, a particle accelerator, a nuclear fusion experiment apparatus, etc.
2. Description of the Related Art
Conventionally, in a semiconductor manufacturing apparatus, for example, operations, such as etching and sputtering, are performed in a high-vacuum semiconductor process chamber. Generally speaking, to create a high vacuum from atmosphere in a container of such a semiconductor process chamber, a combination of a high-vacuum pump and a low-vacuum pump is adopted. However, since each of the two pumps are rather large, they are hard to be integrated with each other, and it is impossible to unite them into a single small vacuum pump.
Japanese Patent Laid-open No. 88624/1985 discloses a known vacuum pump in which it is possible to effect evacuation from the atmospheric pressure to the molecular flow range with a single pump. In the vacuum pump disclosed in this publication, however, an open-type impeller is used, so that it is only possible to achieve a degree of vacuum of approximately 10xe2x88x923 Pa. Further, a high evacuation rate cannot be achieved at a pressure close to the atmospheric pressure.
The present invention has been made with a view to solving the above problems. It is an object of the present invention to provide a small vacuum pump which makes it possible to efficiently create a high vacuum (degree of vacuum: 10xe2x88x925 Pa) from the atmosphere by using a single unit of this pump.
To achieve the above object, there is provided, in accordance with the present invention, a vacuum pump including a turbo-molecular pump mechanism portion performing an evacuating operation through interaction between rotating rotor blades and stationary stator blades, a thread groove pump mechanism portion performing an evacuating operation through interaction between a rotating rotor and a thread groove, and a volute pump mechanism portion performing an evacuating operation through rotation of a volute impeller, wherein the turbo-molecular pump mechanism portion is arranged on a high vacuum side, the volute pump mechanism portion is arranged on an atmosphere side, and the thread groove pump mechanism portion is arranged between the turbo-molecular pump mechanism portion and the volute pump mechanism portion.
Further, in accordance with the present invention, there is provided a vacuum pump characterized in that the rotor blades of the turbo-molecular pump mechanism portion, the rotor of the thread groove pump mechanism portion, and the impeller of the volute pump mechanism portion are integrally mounted to a single rotor shaft, the rotor shaft being rotated by a single motor.